Tell mount to re-scan fstab and mount the new directories automatically:
mount -a

(optional) Manual mount: If you do not want the system to mount these directories at boot, they can instead be mounted by hand. Note that this will need to be repeated each time the system is rebooted:
mount -o bind /tmp /var/chroot/tmp
mount -t proc proc-chroot /var/chroot/proc
mount -t devpts devpts-chroot /var/chroot/dev/pts

Copy your /etc/resolv.conf:
cp /etc/resolv.conf /var/chroot/etc/

As the user who started X11:
xhost + # assuming you are behind NAT

Start the chroot environment (as root again):
dchroot -d -c Openmoko # -d to take the environment variables with you

Tell mount to re-scan fstab and mount the new directories automatically:
mount -a

(optional) Manual mount: If you do not want the system to mount these directories at boot, they can instead be mounted by hand. Note that this will need to be repeated each time the system is rebooted:
mount -o bind /tmp /var/chroot/tmp
mount -t proc proc-chroot /var/chroot/proc
mount -t devpts devpts-chroot /var/chroot/dev/pts

Copy your /etc/resolv.conf:
cp /etc/resolv.conf /var/chroot/etc/

As the user who started X11:
xhost + # assuming you are behind NAT

Start the chroot environment (as root again):
dchroot -d -c Openmoko # -d to take the environment variables with you